stonewort

from WordNet (r) 3.0 (2006)

stonewort
    n 1: any of various submerged aquatic algae of the genus Chara
         having nodes with whorled filamentlike branches; usually
         encrusted with calcium carbonate deposits

from The Collaborative International Dictionary of English v.0.48

Stonewort \Stone"wort`\, n. (Bot.)
   Any plant of the genus Chara; -- so called because they are
   often incrusted with carbonate of lime. See {Chara}.
   [1913 Webster]

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